Nanotechnology for water disinfection application gains increasing attention. Diatomite is one kind of safe natural material, which has been widely used as absorbent, filtration agents, mineral fillers, especially in water treatment industry. Nanosilver/diatomite nanocomposites were developed in this publication with a facile, effective in-situ reduction method. The as-prepared nanosilver/diatomite nanocomposites demonstrated amazing antibacterial properties to gram-positive and gram-negative bacteria. The corresponding property has been characterized by UV-vis absorbance, Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX) and X-ray Photoelectron Spectroscopy (XPS). Moreover, the detailed bacteria killing experiments further displayed that 0.5 g of the nanosilver diatomite could kill >99.999% of E. Coli within half an hour time. And the silver leaching test demonstrated that the concentrations of silver in the filtered water under varies pH environment were below the limit for silver level of WHO standard. Considering the low price of natural diatomite, it is believed that the nanosilver/diatomite nanocomposites have potential application in water purification industry due to its excellent antimicrobial property. (C) 2016 Elsevier B.V. All rights reserved.